抄録
Observation is made on the following remarkable properties of rectangular glass rod revealed by instantaneous photographs of fracturing when shot tranversely by bullets with impact velocities of 230 and 400 m/sec.
(1) There are two kinds of fracturing: one is the fracture progressing from the point of impact in zigzag course which is considered due to transverse stress wave (named zigzag fracture), and the other is the fracture developing in reverse direction from the free end to the point of impact by longitudinal stress wave.
(2) The zigzag fracture is due to the repetition of restitution force taking place as thefracture progresses.
(3) Propagation velocity of zigzag fracture is approximately 2600 m/sec. and that of fracture itself is approximately 2850 m/sec.
(4) Unaffected region is observed close to the free end resulting from the interference of incident and reflected pulse waves at the boundary surface.
(5) Fracturing is little affected by the change of impact velocity.
